Glass Fiber-Reinforced Concrete

Glass fibers have relevance in civil engineering applications because of cost and specific strength properties. The worldwide glass reinforcement market is estimated in 2.5 million tons (2001), with an average growth of 5.4% per year [9]. Original GFRC pastes used conventional borosilicate glass fibers (E-glass) and soda-lime-silica glass fibers (A-glass), which lose strength due to high alkalinity (the pH value for concrete environ­ment is above 12.8 [10]) of the cement-based matrix. Other compositions include S-glass (an Mg-Al-silicate of high strength), S-2 glass (an S-glass composition with surface treatment), and C-glass (a Na-borosilicate) used in corrosive environments [8]. Improved alkali-resistant fibers have compositions containing 16% zirconia. Another potential alternative is the use of novel high-alkaline-resistant Fe-phosphate glasses [11]. Extended exposure of silica-based GFRC to natural weather results in changes in mechanical properties and volumetric dimension changes. Dimensional changes in GFRC can be considerably greater than those of conventional concrete, as a result of the high cement content in the mortar matrix. Over stressing or stress concentrations can cause cracks. This can be critical in components that are overly restrained.

Table 2 Applications of GFRC [7] General Area Examples

Подпись: Agriculture Architectural Asbestos replacement Ducts and shafts Fire protection Buildings Housing Marine Metal placement Pavements Permanent and temporary Site-applied surface bonding Small buildings Small containers Street furniture Water applications Irrigation channels, reservoir linings Interior panels, exterior panels, door frames, windows Sheet cladding, plain roof tiles, fire-resistant pads, molded shapes and forms, pipes

Track-side ducting for cables, internal service ducts Fire doors, internal fire walls, partitions, calcium silicate insulation sheets Roofing systems, lintels, cellar grills, floor gratings, hollow nonstructural columns, impact-resistant industrial floors, brick fagade siding panels Single and double skin cladding, prefabricated floor and roof units Hollow buoys, floating pontoons, marina walkways, workboats Sheet piling for canal, lake or ocean revetments, covers, hoods, stair treads Overlays

Bridge decking formwork, parapets, abutments, waffle forms, columns and beams

Bonding of dry-blocks walls, single skin surface bonding to metal lath substrates, ultra-low-cost shelters Sheds, garages, acoustic enclosures, kiosks, telephone booths Telecommunication boxes, storage tanks, meter encasements, utility boxes Seats and benches, planters, litter bins, signs, noise barriers, bus shelters Low-pressure pipes, sewer linings, field drainage components, tanks

Fiber is used in larger dosages, i. e., ~2 kg m-3 of concrete in commercial appli­cations. The single largest application of GFRC has been the manufacture of exterior building facade panels [12], with at least 80% of all GFRC architectural and structural components manufactured in the US Other application areas are listed in Table 2.